Hepatic involvement in aggressive systemic mastocytosis (ASM) is relatively common, and the main clinical features of this disease include hepatomegaly, portal hypertension, ascites, and fibrosis. Cirrhosis is a rare ASM symptom. We report an ASM case that initially mimicked cirrhosis based on clinical and radiographic analyses. The portal tract was expanded by mononuclear inﬂammatory cells, and an increase in collagen amount was observed in routine histological sections of the biopsied liver. A diagnosis of systemic mastocytosis (SM) was made after ancillary tests for mast cells using bone marrow aspirates. Extensive involvement of the liver and gastrointestinal tract was observed. Clinicians and pathologists need to consider ASM as a diagnosis or differential diagnosis in a clinical case of cirrhosis with unknown etiology. The diagnosis can be confirmed or disregarded by immunohistochemical staining and molecular analysis.